Question

NT4-1. 3 pts. A beef stick manufacturing plant proposed to discharge saline (salty) wastewater to a river. Upon reviewing the proposal, the governing regulatory agency set a 200 mg/L salt maximum level in the river downstream of the discharge point. In response the manufacturing plant proposed adding desalination equipment between the manufacturing plant and the river to remove enough salt from the wastewater to meet the regulatory requirement, 15% of the wastewater flow becomes brine (concentrated salt), a byproduct from the desalting unit that flows to evaporation/drying ponds. Additional information is provided below Flowrate, Qw 500 m/day Salt concentration, Cw 28,000 mg/L (Initial, no treatment) river Flow rate, QT,-? Salt concentration, CTW-? River: of mixing zone Flowrate Salt conc. 200 mg/L RU 24,000 m'/day CRU 20 mg/L RD RD Questions: a) How much of the plant wastewater ends up flowing into the river Qrw)? (in m/d) b) What is the concentration of salt in the treated wastewater (Cw)? ? How How much salt is discharged to the river each day (kg/d much salt is discharged to the evaporation ponds day (kg/day)? Begin by creating a flow diagram of the system. Then balance flow volume, first in the de-salter unit and then in the mixing zone where treated wastewater discharges into the river. Now balance salt. Performing the balances in this order is the most efficient approach. Assume perfect mixing and steady-state conditions. The salt is non-reactive

Answer 1